With the increasing use of the organic base substrates for providing circuit patterns, greater demands have been placed on the product performance of these circuit patterns, and thus on the organic substrates. These circuit patterns may be formed by various means. An electroless metal deposition method has become increasingly more attractive for forming these patterns.
In general, the closest related process to this invention is an electroless process for depositing a metal such as a noble metal on an organic base. According to the prior art, the process consists of treating the base to accept a catalyst such as a palladium complex or salt in conjunction with a sensitizer therefor, which can be reduced thereafter by photolytic methods thereby rendering the exposed area auto-catalytic to an electroless plating bath. An appropriate illustration of such a method and other prior art methods are shown in U.S. Pat. No. 3,562,005 issued Feb. 9, 1971.
The pattern which can be obtained in the sensitized substrate is obtained by masking selective particular catalyst placement, which is then used as a means to obtain a circuit pattern in an electroless metal deposition bath, and thereafter, if needed by an electrolytic process. The various disadvantages and advantages of the above and competing methods are discussed in U.S. Pat. No. 3,562,005 and need not be repeated herein. Although polyimide films have been treated with hydrazine before, e.g., U.S. Pat. No. 3,395,057, the photolytic, or catalytic activity of the thus treated surface has not been known with respect to modifying surface properties of polyimide polymers for rendering the surface photolytically active.